1. Technical Field
The present disclosure relates to a metal clad laminate useful for a flexible printed circuit board, and a preparation method thereof. The present disclosure further relates to a method for preparing a flexible printed circuit board by using the metal clad laminate.
2. Description of the Related Art
A flexible printed circuit (FPC) board, due to its flexibility and bendability, enables three-dimensional wiring through adaptation to the size and shape of the product, and also is characteristically light and thin, making it one of the essential components in various high-tech devices such as cameras, video cameras, displays, disk drives, printers, mobile phones and other such devices.
A flexible metal clad laminate, for example, flexible copper clad laminate (FCCL), is an upstream material for a flexible printed circuit board. The existing FCCLs may be divided, in light of their structures, into three-layer FCCLs (3L FCCLs) with adhesive and two-layer FCCLs (2L FCCLs) without adhesive. The 3L FCCL is mainly formed by adhering a copper foil onto a polyimide layer by using an epoxy or acrylate resin adhesive as an intermediate layer. The 2L FCCL is made by a special process, contains no low heat-resistant adhesives such as epoxy or acrylate resins, and is thus more reliable. Moreover, 2L FCCL is better suited to development of thinner products, and thus is gradually replacing 3L FCCL in practice.
The FCCLs may be divided, in light of the circuit configuration requirements of the products (e.g., printed circuit boards), into single-sided and double-sided FCCLs. Single-sided FCCL is the most fundamental FCCL. It has a copper foil layer useful for circuit formulation clad only on one side thereof. Single-sided FCCL has the advantages of easy fabrication process, low cost, and good flexibility. Double-sided FCCL has a copper foil layer clad on both upper and lower sides. Accordingly, circuits may be formed on both sides of the double-sided FCCL, and may electrically connect to each other by a via hole. Therefore, double-sided FCCL can achieve a higher integration, is beneficial to controlling electrical resistance, and is useful for circuit fabrication simultaneously on both sides, so as to save time, but may suffer from potential poor flexibility due to greater thickness.
Single-sided FCCL has advantages such as being light, thin, and highly flexible. Double-sided FCCL has advantages such as good mechanical performance, electrical characteristics (e.g. low dielectric constant), and capacity for forming circuits on both sides. However, it is usually difficult for researchers in the art of FCCLs to pursue good operability while maintaining the above advantages at the same time. Therefore, there is still a need in the art for a FCCL that is light, thin and highly flexible, has good electrical characteristics, and requires less time and expense on subsequent processing.